This invention relates to a screw press machine used to devolatilize various materials, e.g., elastomeric, thermoplastic, and the like, wherein the materials supplied to the press contain a significant quantity of some volatilizable substance, such as a hydrocarbon solvent, or water, and the material is mechanically worked and heated within the press, raising the substance to a temperature at which it will volatilize, whereupon the substance is released under some pressure as a gas or vapor, and is separated from the material and conducted away from the press.
A typical form of apparatus of this general type, particularly adapted for the removal of hydrocarbon solvents, is shown in U.S. Pat. No. 3,684,252 issued Aug. 15, 1972, to The French Oil Mill Machinery Company. A related U.S. Pat. No. 3,683,511 issued Aug. 15, 1972, to The Firestone Tire & Rubber Company, discloses and claims a method of removing volatile hydrocarbons from an elastomer, utilizing such equipment. A related patent, which deals in greater detail with the preparation and handling of the elastomer prior to its introduction into the screw press equipment is disclosed in U.S. Pat. No. 3,799,235 issued Mar. 26, 1974, also to The Firestone Tire & Rubber Company.
A venting system for equipment of this type, wherein the vent from the press is provided with a particular design of screw mechanism to control the exit flow of removed vapors, and to avoid entrainment therein of particles of material, is disclosed in U.S. Pat. application Ser. No. 856,103 filed concurrently herewith, entitled "Screw Vent ", discloses a venting system for the regions of the press equipment where substantial quantities of the volatilizable substance have already been removed. The present invention deals with a simplified venting system for the upstream sections of the screw press apparatus, where initially larger quantities of the volatilizing substances are being removed, and wherein the handling of particles of the material, sometimes referred to as "fines," can be dealt with in somewhat different manner. At the same time, the substantial quantities of a volatilizable substance are removed in such a manner as to avoid the occurrence of unusually high vapor pressure within the press which might result in gasses passing by and damaging mechanical seals of the screw press shaft, thus leading to leakage of materials through those seals.
An extruder for concentrated polymers (30-80% polymer, 70-20% solvent by weight) is disclosed in U.S. Pat. No. 3,963,558 issued June 15, 1976, incorporating a so-called rear vent. This vent is located upstream of the inlet to the extruder from a concentrator via a screw conveyor, and is intended to vent solvent vapor through very shallow inter-flight spaces at the rear end of the extruder screw. However, the shallow space between the screw body, flight, and barrel tends to accelerate the outflow of venting vapors, and no provision is made to counteract the tendency of polymeric material to creep backward along the screw, and for particles of the material to be entrained in the venting vapors. This can quickly lead to deposits and/or clogging of the vent or a pipe extending from it, or can create a deposit and cleaning problem elsewhere if the vent and pipe pass the vapor entrained particles.